It is common to employ annular apparatus, including an antenna, for electronically transmitting tire or wheel identification or other data at radio frequency. The apparatus includes a radio-frequency transponder comprising an integrated circuit chip having data capacity at least sufficient to retain identification information for the tire or wheel. Other data, such as the inflation pressure of the tire or the temperature of the tire or wheel at the transponder location, can be transmitted by the transponder along with the identification data.
As is evidenced by the references described below incorporated herein by reference, it is known in the art to employ an annular antenna to transmit, at radio frequencies, data from a transponder contained within the structure of a tire or tire and wheel assembly. The antenna and transponder may be incorporated into a tire during “pre-cure” manufacture. In practice, however, it is very difficult to do this. Both radial ply and bias ply tires undergo a substantial diametric enlargement during the course of manufacture. Bias ply tires are expanded diametrically when inserted into a curing press, which typically has a bladder that forces the green tire into the toroidal shape of the mold enclosing it. Radial ply tires undergo diametric expansion during the tire building or shaping process and a further diametric expansion during the course of curing. Any annular antenna and the electronic circuitry associated therewith built into the tire must be able to maintain structural integrity and the mechanical connection between the antenna and transponder package during the diametric enlargement of the tire during its manufacture. Once assembled into the tire, any detected malfunction in the antenna, transponder, or antenna to transponder connection that cannot be repaired destroys the utility of the tire and may necessitate a scrapping of the tire. Hence, placement of an annular antenna-transponder assembly into a tire during its manufacture carries risk that subsequent failure or breakage of assembly components will necessitate the destruction of the otherwise suitable host tire.
Not only is the risk of damage to an annular antenna-transponder system present during its incorporation into a tire during manufacture, but damage to such systems are not uncommon from operation of the tire on a vehicle. Loop antennas in known tire pressure monitoring systems have heretofore been placed into the tire during the curing process either at the crown of the tire, the bead of the tire, or the sidewall. Antennas and transponders located in the crown are subjected to substantial compressive strain and at the sidewall a high strain amplitude. Such locations represent high load and deformation regions of the tire. Consequently, antenna, transponders, and the connections therebetween in such locations are prone to breakage and mechanical or electrical failure.
Other issues relevant to mounting a transponder module in a tire include replacing the entire transponder module if it requires replacement and, in the case of battery-powered (“active”) transponders, replacing the battery if required. Preferably, the transponder, whether “active” or “passive” should represent only a fractional cost of the overall tire. Hence, replacing an entire tire because of an inoperative transponder would be highly undesirable. In the case of permanently embedding the transponder within the tire, such as is shown at FIG. 13 of U.S. Pat. No. 5,500,065, replacing the transponder unit or any component thereof is a virtual impossibility.
U.S. Pat. No. 5,181,975 discloses a number of locations and techniques for mounting a transponder within a tire. In a tire that has already been manufactured, the transponder may be attached to the axially inner side of the inner liner or to the axially outer side of the tire sidewall by means of a tire patch or similar material or device. U.S. Pat. No. 5,218,861 also discloses locations and techniques for mounting an integrated circuit transponder and pressure transducer within a pneumatic tire. The common problem shared in each prior art approach is that the transponder and antenna represent a system. For best magnetic coupling and to enable a 360 degree continuous read, it is desirable for the antenna to be annular The manner of establishing an effective and mechanically secure coupling between a transponder and annular antenna is problematic and a satisfactory solution is not found in the art.
A final design challenge is to provide a standard platform capable of accommodating the wide variety of transponders and various types and sizes of pneumatic tires commercially available in the industry. Optimally, a standardized annular apparatus would accept components of different manufacturers and such uniformity in the annular system platform would serve to enhances its commercial acceptance.
It is another aspect of the invention to provide method and apparatus for mounting a transponder module in a pneumatic tire in such a manner that the transponder may conveniently be inserted, removed, replaced and/or maintained, either during tire manufacture or after. Additionally, the annular apparatus and method of employing same would operate to optimally locate the transponder sensors within a tire cavity to facilitate accurate measurement.
It is another aspect of the present invention to provide method and apparatus for mounting a transponder and an antenna for the transponder within a pneumatic tire, and to provide for a mechanically decoupled relationship between the transponder and the antenna.
It is another aspect of the invention to provide a method for mounting a transponder module in a pneumatic tire at any point in the tire manufacturing process, with minimal impact on tire performance.
One of the two spaced-apart metallic beads of a tire can satisfy the requirement of a large-diameter transformer primary winding mounted within a tire as described in U.S. Pat. No. 5,181,975 and U.S. Pat. No. 5,218,861. The disadvantage is that while the bead location in a tire represents a low load and deformation region, this advantage is countered by the undesirable electromagnetic influence associated with the electrically conductive metallic wheel upon which the tire is mounted and to which the bead is closely adjacent. Consequently, location of the antenna-transponder assembly at the bead may protect the assembly from resulting strain from tire operation but communication quality may prove unsatisfactory due to interference problems attendant such a location.
Moving the antenna away from the bead region of the tire to the crown area, as taught by PCT Application WO 99/29525 avoids magnetic interference caused by the wheel rim but places the antenna in a high strain region. Consequent damage to the antenna from tire operation can result.
Depending on the RF generator, the transponder or other electronic devices involved, and input power requirements of the system, the antenna must also meet certain conductivity requirements as well as the mechanical requirements summarized previously. The cable construction of choice is one or more wires composed of copper, copper-clad steel, aluminum, or any other highly conductive metal. The wire for the antenna must have minimal electrical resistance so as to minimize power losses and signal transmission losses. In passive systems where power is supplied to the transponder package by a magnetic coupling between the antenna and a transponder coil, the antenna and antenna to transponder coupling must also facilitate a high energy transfer.
U.S. Pat. No. 4,319,220 discloses a system for monitoring tire pressure comprising wheel units in the tires and a common receiver. U.S. Pat. No. 6,147,659 discloses the use of metallic component members in a tire as an antenna directly connected to a transponder. U.S. Pat. No. 4,074,227 discloses a tire pressure indicator for a tire and includes a transponder coupled to a signal coil that is disposed as a circular loop about the tire. U.S. Pat. No. 5,491,483 discloses a single loop annular antenna mechanically and magnetically coupled to a transponder through an impedance transformer. U.S. Pat. No. 5,479,171 discloses a double coupled transponder and antenna assembly for a tire in which the antenna is mounted about the perimeter of a tire and includes a coupling coil at one end. A transponder is located in close proximity and is loosely coupled to the coil. Similarly, U.S. Pat. No. 5,270,717 discloses an RF-ID transponder having a long antenna coupled to a transponder by a loose coupling coil. U.S. Pat. No. 5,304,172 B discloses a tire inflation pressure monitoring system that includes a loop antenna coupled to a receiver. U.S. Pat. No. 6,062,072 discloses a tire pressure monitoring system that includes a transmitter having an antenna with several windings which are integrated into the side walls or tread region of a tire. PCT Application No. PCT/US97/22470 discloses an annular apparatus that may be incorporated in a ring of elastomeric material attached to the rim or embedded in the tire at its equatorial plane. U.S. Pat. No. 4,911,217 discloses a tire transponder and signal transmitter. U.S. Pat. No. 5,181,975 discloses a tire transmitter using the bead of the tire as a primary transformer winding. U.S. Pat. No. 5,218,861 discloses a transponder for a tire having a coil antenna. U.S. Pat. No. 6,228,929 discloses a tire comprising a strip of electrically conductive rubber. U.S. Pat. No. 6,255,940 teaches a patch mounted tire tag. U.S. Pat. No. 6,369,712 discloses an adjustable temperature sensor for a tire. PCT Application No. PCT/US99/1866 discloses a transponder and coupling element for a tire. PCT Application No. PCT/US99/20271 discloses a tire monitoring system. PCT Application No. PCT/US99/27094 discloses a transponder and antenna apparatus for pneumatic tires. PCT Application No. PCT/US99/18610 discloses a tire monitoring system including an annular antenna. PCT Application No. PCT/US97/22463 discloses an annular apparatus for a tire including an antenna embedded in the tire at its equatorial plane.
While the prior art listed above functions well and represents several viable approaches toward meeting the needs of the industry, certain deficiencies inherent in each approach prevent the collective prior art from achieving a satisfactory system, assembly, and method for mechanically integrating an annular antenna-transponder system into a tire. The prior art teaches antenna to transponder coupling techniques that achieve a less than satisfactory coupling factor. Moreover, the prior art presents less durable than desired transponder to loop connections that are, in general, complicated to effect and prone to breakage during tire manufacture and operation. Additionally, the prior art methods of incorporating an annular antenna-transponder system into a tire do not facilitate a convenient retrofit incorporation of the monitoring system into previously manufactured tires and do not readily allow for easy repair or replacement of the annular assembly or components should the need arise. Finally, existing prior art systems for coupling an annular antenna to a transponder package do not individually or collectively achieve the foregoing mechanical objectives while positioning the apparatus in an optimal location on or in a tire.